Add API for setting/getting native state

Summary:
Add API for setting/getting native state.

When present, the internal NativeState property of an object always stores a NativeState with a pointer to a heap-allocated shared_ptr + a finalizer that simply `delete`s it.

Changelog:
[Internal][Added] - JSI API for setting/getting native state on a JS object

Reviewed By: jpporto

Differential Revision: D36499239

fbshipit-source-id: a1ff1905811db1aac99ece3f928b81d0abfb342b

ReactCommon/jsi/JSCRuntime.cpp

@@ -168,6 +168,12 @@ class JSCRuntime : public jsi::Runtime {
       const jsi::Object &) override;
   jsi::HostFunctionType &getHostFunction(const jsi::Function &) override;
 
+  bool hasNativeState(const jsi::Object &) override;
+  std::shared_ptr<jsi::NativeState> getNativeState(
+      const jsi::Object &) override;
+  void setNativeState(const jsi::Object &, std::shared_ptr<jsi::NativeState>)
+      override;
+
   jsi::Value getProperty(const jsi::Object &, const jsi::String &name) override;
   jsi::Value getProperty(const jsi::Object &, const jsi::PropNameID &name)
       override;
@@ -862,6 +868,21 @@ std::shared_ptr<jsi::HostObject> JSCRuntime::getHostObject(
   return metadata->hostObject;
 }
 
+bool JSCRuntime::hasNativeState(const jsi::Object &) {
+  throw std::logic_error("Not implemented");
+}
+
+std::shared_ptr<jsi::NativeState> JSCRuntime::getNativeState(
+    const jsi::Object &) {
+  throw std::logic_error("Not implemented");
+}
+
+void JSCRuntime::setNativeState(
+    const jsi::Object &,
+    std::shared_ptr<jsi::NativeState>) {
+  throw std::logic_error("Not implemented");
+}
+
 jsi::Value JSCRuntime::getProperty(
     const jsi::Object &obj,
     const jsi::String &name) {

ReactCommon/jsi/jsi/decorator.h

@@ -222,6 +222,17 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
     return dhf.target<DecoratedHostFunction>()->plainHF_;
   };
 
+  bool hasNativeState(const Object& o) override {
+    return plain_.hasNativeState(o);
+  }
+  std::shared_ptr<NativeState> getNativeState(const Object& o) override {
+    return plain_.getNativeState(o);
+  }
+  void setNativeState(const Object& o, std::shared_ptr<NativeState> state)
+      override {
+    plain_.setNativeState(o, state);
+  }
+
   Value getProperty(const Object& o, const PropNameID& name) override {
     return plain_.getProperty(o, name);
   };

ReactCommon/jsi/jsi/jsi-inl.h

@@ -202,6 +202,24 @@ inline std::shared_ptr<HostObject> Object::getHostObject<HostObject>(
   return runtime.getHostObject(*this);
 }
 
+template <typename T>
+inline bool Object::hasNativeState(Runtime& runtime) const {
+  return runtime.hasNativeState(*this) &&
+      std::dynamic_pointer_cast<T>(runtime.getNativeState(*this));
+}
+
+template <typename T>
+inline std::shared_ptr<T> Object::getNativeState(Runtime& runtime) const {
+  assert(hasNativeState<T>(runtime));
+  return std::static_pointer_cast<T>(runtime.getNativeState(*this));
+}
+
+inline void Object::setNativeState(
+    Runtime& runtime,
+    std::shared_ptr<NativeState> state) const {
+  runtime.setNativeState(*this, state);
+}
+
 inline Array Object::getPropertyNames(Runtime& runtime) const {
   return runtime.getPropertyNames(*this);
 }

ReactCommon/jsi/jsi/jsi.cpp

@@ -81,6 +81,8 @@ void HostObject::set(Runtime& rt, const PropNameID& name, const Value&) {
 
 HostObject::~HostObject() {}
 
+NativeState::~NativeState() {}
+
 Runtime::~Runtime() {}
 
 Instrumentation& Runtime::instrumentation() {

ReactCommon/jsi/jsi/jsi.h

@@ -128,6 +128,13 @@ class JSI_EXPORT HostObject {
   virtual std::vector<PropNameID> getPropertyNames(Runtime& rt);
 };
 
+/// Native state (and destructor) that can be attached to any JS object
+/// using setNativeState.
+class JSI_EXPORT NativeState {
+ public:
+  virtual ~NativeState();
+};
+
 /// Represents a JS runtime.  Movable, but not copyable.  Note that
 /// this object may not be thread-aware, but cannot be used safely from
 /// multiple threads at once.  The application is responsible for
@@ -296,6 +303,12 @@ class JSI_EXPORT Runtime {
   virtual std::shared_ptr<HostObject> getHostObject(const jsi::Object&) = 0;
   virtual HostFunctionType& getHostFunction(const jsi::Function&) = 0;
 
+  virtual bool hasNativeState(const jsi::Object&) = 0;
+  virtual std::shared_ptr<NativeState> getNativeState(const jsi::Object&) = 0;
+  virtual void setNativeState(
+      const jsi::Object&,
+      std::shared_ptr<NativeState> state) = 0;
+
   virtual Value getProperty(const Object&, const PropNameID& name) = 0;
   virtual Value getProperty(const Object&, const String& name) = 0;
   virtual bool hasProperty(const Object&, const PropNameID& name) = 0;
@@ -711,6 +724,25 @@ class JSI_EXPORT Object : public Pointer {
   template <typename T = HostObject>
   std::shared_ptr<T> asHostObject(Runtime& runtime) const;
 
+  /// \return whether this object has native state of type T previously set by
+  /// \c setNativeState.
+  template <typename T = NativeState>
+  bool hasNativeState(Runtime& runtime) const;
+
+  /// \return a shared_ptr to the state previously set by \c setNativeState.
+  /// If \c hasNativeState<T> is false, this will assert. Note that this does a
+  /// type check and will assert if the native state isn't of type \c T
+  template <typename T = NativeState>
+  std::shared_ptr<T> getNativeState(Runtime& runtime) const;
+
+  /// Set the internal native state property of this object, overwriting any old
+  /// value. Creates a new shared_ptr to the object managed by \p state, which
+  /// will live until the value at this property becomes unreachable.
+  ///
+  /// Throws a type error if this object is a proxy or host object.
+  void setNativeState(Runtime& runtime, std::shared_ptr<NativeState> state)
+      const;
+
   /// \return same as \c getProperty(name).asObject(), except with
   /// a better exception message.
   Object getPropertyAsObject(Runtime& runtime, const char* name) const;